Display devices commonly used in market are separate-type touch screens in which a touch panel and a liquid crystal panel are manufactured separately and then are assembled together. The display device manufactured in this way is relative thick and has significantly decreased transmittance and contrast since several layers of glass and film are introduced. In addition, the cost for the manufacture is high. To make the liquid crystal display device with a touch panel with smaller thickness, better display effect and more desirable cost, embedded touch technology is proposed, in which the touch panel and the liquid crystal panel are integrated, where the touch panel may use capacitive touch technology, resistive touch technology or infrared touch technology, etc., and a structure of the liquid crystal panel may be in a common twisted nematic liquid crystal (TN) mode, an in plane switching liquid crystal (IPS) mode or a fringe field switching liquid crystal (FFS) mode, etc. At present, the embedded touch technology mainly has two trends.
One is on-cell (outside liquid crystal cell) embedded touch display device, in which touch sensors are disposed between a color film substrate and a polarizer. Each liquid crystal panel and each touch assembly need to be assembled through lamination, and the final assembly cost depends on not only the cost of material but also yield of lamination process. Improving lamination yield and reducing number of times of lamination will be main stream in technology development of such touch panel.
The other is in-cell (inside liquid crystal cell) embedded touch display device, in which the touch sensors are embedded into liquid crystal pixels. For the in-cell embedded touch display device, touch sensing elements may be manufactured with a standard thin film transistor (TFT) liquid crystal display (LCD) process, and the lamination for the appearance and the alignment of mechanisms in the display device are avoided, resulted in lighter and thinner products with largely reduced weight and thickness, barely changed viewing angle, better transmittance for the panel and better image quality for the screen.
In general, the performance of existing in-cell (inside liquid crystal cell) embedded touch display device is unsatisfactory.